Refrigerating system having defrosting arrangement



March 6, 1956 L. A, PH|| |PP 2,737,030

REFRIGERATING SYSTEM HAVING DEFROSTING ARRANGEMENT Filed Deo. 21', 19512 sheets-sheet 2 INVENToR. [nuff/vr: ,4 Fly/mv Arran/vn REFRIGERATINGSYSTEM HAVING DEFROSTING ARRANGEMENT Lawrence A. Philipp, Detroit,Mich., assigner to Naslb Kelvinator Corporation, Detroit, Mich., acorporation of Maryland Application December 21, 1951, Serial No.262,809

1 Claim. (Cl. 62-116) This invention relates to refrigerating apparatusand more particularly to the arrangement for defrosting the refrigerantevaporator of the cooling system thereof.

One of the objects of my invention is to provide a new and improvedmethodV for the self defrosting of a refrigerator.

Another object of my invention is to provide a new and improved methodfor defrosting the evaporator of a refrigerating system by increasingthe pressure therein, causing liquid refrigerant during the period ofsaid increased pressure to flow to and through said evaporator to themotor-compressor unit, utilizing the motor-compressor unit to evaporatesaid liquid refrigerant, andthen conduct the latent heat of suchevaporation by conducting the evaporated refrigerant to said evaporator.

Another object of my invention is to provide a new and improvedarrangement for automatically defrosting a refrigerating system for arefrigerator which includes utilizing inherent characteristics of thesystem without the aid of additional or extraneous heating elements.

Another object of my invention is to provide a refrigerating systemincluding a motor-compressor unit and a refrigerant evaporator with anunrestricted flow between the outlet of the evaporator and themotor-compressor unit and a by-pass conduit around the liquid supplymeans to the evaporator and to periodically operate the by-pass meanseither by a timer or counting mechanism to cause the motor-compressorunit to increase the pressure in the evaporator to drive some of theliquid therethrough and conduct same to the motor-compressor unit toevaporate said liquid refrigerant and conduct such evaporatedrefrigerant to said evaporator to rapidly defrost same.

Another object of my invention is to provide a refrigerating systemwherein the evaporator is constructed to retain some liquid refrigeranttherein during normal operation of the refrigerating system and to makeprovisions for increasing the pressure in the evaporator and equalizingthe pressure throughout said system during periods when it is desired todefrost the evaporator so that the increased pressure and velocity ofthe refrigerant entering the evaporator will cause some liquid to flowfrom the outlet of the evaporator into the motor-compressor unit housingwhere it is evaporated to further increase the pressure and temperaturein the system by the latent heat of evaporation to rapidly defrost theevaporator.

Another object of my invention is to provide a refrigerating systemwherein liquid refrigerant during normal operation is stored in arefrigerant receiver or accumulator and during defrosting time suchliquid refrigerant is delivered to the evaporator at an increasedpressure so that some liquid overflows the evaporator and is driven intothe condensing element to be evaporated and the latent heat ofevaporation is conducted to the evaporator to rapidly defrost same.

It is another object of my invention to provide an improved arrangementfor controlling the automatic defrosting period for defrosting therefrigerating system and 2,737,030 Patented Mar. 6, 1956 ICC therestoration of normal operation upon completion of such defrostingperiod.

Another object of my invention is to provide an improved refrigerantevaporator wherein liquid refrigerant is stored in both an inletaccumulator and an outlet accumulator during the cooling operation ofthe evaporator to aid in the cooling function of the evaporator.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein preferred forms of the present invention are clearlyshown.

In the drawings:

Fig. 1 is a front view of a refrigerator embodying features of myinvention and showing a portion thereof broken away;

Fig. 2 is a side view of the refrigerator shown in Fig. 1 and showing aportion thereof broken away;

Fig. 3 is a layout View of a portion of a refrigerant evaporatorembodying features of my invention and showing the evaporator in theflat before same is bent to form a box-like structure;

Fig. 4 is a diagrammatic illustration of the refrigerating systemembodying features of my invention with an isometric illustration of theevaporator;

Fig. 5 is a rear view of a portion of the evaporator shown in Fig. 4 andshowing a modified system of control elements attached to the evaporatorand embodying features of my invention;

Fig. 6 is a rear view of an evaporator showing a modified form ofrefrigerant receiving and storage passages and showing the latter incross section;

Fig. 7 is a further modified form of a refrigerant evaporator showingthe refrigerant storage passage in cross section;

Fig. 8 is a modified form of a refrigerant motor-compressor unitembodying features of my invention; and

Fig. 9 is a still further modified form of motor-compressor unitembodying features of my invention.

In accordance with my invention I provide an improved arrangement in arefrigerating system for rapidly defrosting the refrigerant evaporatorthereof. My improved arrangement includes utilizing inherentcharacteristics of a refrigerating system to rapidly defrost therefrigerant evaporator thereof. The inherent characteristics of thesystem include utilizing the heat of the motor-compressor unit toevaporate liquid refrigerant which is conducted from the refrigerantevaporator into the motor-compressor casing where the liquid isconducted into thermal or actual contact with the motor-compressor unitand the casing which encloses said unit. This liquid refrigerant isconducted from the evaporator which is so designed as to retain allliquid refrigerant within the refrigerant flow passages including theaccumulator thereof during normal operation of the refrigerating systemand to conduit liquid refrigerant from the evaporator to themotor-compressor unit when the pressure in the evaporator is increased.Thus a change in velocity and pressure causes liquid refrigerant to bedriven from the evaporator into the vapor return conduit which isconnected to the interior of the motor-compressor casing. The increasein pressure and the increase in velocity takes place automatically by atiming or counting device which opens a by-pass around the refrigerantcondenser and supply conduit to permit compressed gas to flow into theevaporator thus increasing the pressure and temperature therein andincreasing the velocity of the refrigerant passing therethrough. Myinvention also includes the provision of a receiver or accumulator atthe outlet of the liquid supply means so that some liquid is retained inthe receiver during normal operation and when the system isautomatically placed in condition for defrost, this liquid retained inthe receiver is circulated through the evaporator into the unrestrictedavancee supply conduit 26. The conduit 26 is a capillary or smalldiameter tube which controls the ilow of liquid refrigerant from thecondenser to the accumulator 98 to allow -the proper amount of liquid tobe delivered to the evaporator 22 and in so doing establishes a pressuredifferential between the outlet of' the compressor and the interior ofthe evaporator. Liquid refrigerant entering the accumulator 98 atsubstantially lower pressure than that in the condenser will tend to llthe accumulator before passing into and through the conduit 80 of theevaporator 22. As will be noted, the accumulator 98 is placed so thatthe inlet end thereof is much lower than the outlet end :thereof so thatsome liquid will be retained therein during normal operation of therefrigerating system. When the system is originally charged, the amountof liquid is computed so that during normal operation a small amount ofliquid rerefrigerant will be retained in the accumulator 100 but belowthe inlet end of the vapor return conduit 28. Thus during normaloperation only gaseous refrigerant ows from the outlet of accumulator180 of the evaporator 22. This gaseous refrigerant ows through theconduit 28 as previously described herein, which conduit is unrestrictedso that the refrigerant is free to flow without any reduction ofpressure throughout the flow from the evaporator to the motor-compressorunit.

In View of the fact that the two accumulators 98 and i) are in goodthermal contact with the member 96, the sarne tend to aid in coolingfood stored within the evaporator 22 in the same manner as the conduit80. These two accumulators have some liquid therein and act to absorbheat through the member 96 to provide refrigeration at the rear portionof the evaporator 22.

A thermostat 130 of the usual type may be used to control normal cyclingof the refrigerating system. This thermostat includes bellows 132 whichhas connected thereto a thermal bulb 134 which is placed in contact withthe member 82 of evaporator 22. When the evaporator reaches a certainhigh temperature the pressure within the bellows 132 causes the snapacting thermostat 130 to close contacts 136 to initiate operation of themotor-compressor unit 47. When the temperature of the evaporator reachesa certain low point the bellows 132 will contract and cause the snapacting thermostat to open contacts 136 and interrupt the circuit to themotor-compressor unit to cause the motor to stop operating. The circuitto the motorcompressor unit is through line 140 which has contacts 136therein.

In order to maintain operation of the refrigerating system hereindescribed, I have arranged so that defrosting takes place so rapidlythat frozen foods stored within the interior of the evaporator are notpermitted to thaw before the defrosting cycle has been completed and thesystem has been restored to normal operation. This defrosting conditiontakes place strictly automatically by the provision of a clock or timerwhich when once set for the hour of the day desired for operating itwill cause the system to go on defrost automatically at the same houreach day so that the user of the refrigerator need not do anything inorder to have automatic defrosting as the timing device takes care ofinitiating such defrosting cycle and a thermostat control is arranged torestore the system to normal operation when the temperature of theevaporator reaches a predetermined high value. The timing device asherein diagrammatically disclosed is a conventional type of clock 144having an actuating arm 146 which at a certain time of the day engagescontact carrying arm 148 to cause movable contact 150 to engage contact154. This contact carrying arm 148 is frictionally carried in a housing156 so that when the actuating or striking arm 146 engages the contactcarrying arm 148 the contact carrying arm 148 will move the contact 150in engagement with contact 154 to complete the circuit l6 through wires160, 162 and 163 which are connected across the line 140. The member 144is connected across the line 140 by wires 165.

Included in the circuit of wires 162 and 163 is a winding 168 which ispart of a solenoid valve 170. The solenoid valve is connected in aby-pass supply conduit 174 which is connected to the inlet of theaccumulator 98. This by-pass conduit 174 is vof considerably largerdiameter than the small diameter capillary supply conduit 26 and whenthe solenoid valve is moved to open position the refrigerant leaving thecompressor will move directly into the inlet of accumulator 98 toby-pass the condenser conduit 52 and the capillary tube 26.

Preferably the solenoid valve 170 is placed within the insulation 34 ofthe refrigerator and the valve proper thereof is located above the inletto the accumulator 98 so that in the event the valve should move to openposition during a period when the motor-compressor unit is not inoperation, no liquid refrigerant from the accumulator 98 will drain intothe by-pass conduit 174.

When the timer 144 causes contact 150 to engage contact 154 a circuit iscompleted through the solenoid valve to cause such valve to open andwhen the motor-compressor unit is operating, gaseous refrigerant leavingthe compressor flows through the by-pass conduit 174 into the liquidcontaining accumulator 98. Since this refrigerant enters the evaporatorat an increased pressure over that which normally enters the evaporatorthrough the small diameter tube 26 such increased pressure and change ofvelocity causes liquid refrigerant from the accumulator 98 to be forcedthrough the evaporator conduit into the accumulator 100 and causesliquid to overflow said accumulator and to enter the vapor returnconduit 28 which conducts said liquid refrigerant to the outlet end 126of conduit 28 into the cup-shaped portion of the motor rotor 114. Whenthis takes place the liquid refrigerant comes in thermal contact withthe motor-compressor unit and is evaporated by the heat of said unit andthe heat of the casing since some of the liquid entering the cup-shapedportion of the rotor is caused to move upwardly by flash-off and byrotation of the motor to move into contact with the heated casing 110.This causes the liquid refrigerant to evaporate before it enters theinlet 128 of the compressor 116. This evaporated refrigerant is thenconducted to the evaporator where it is utilized to rapidly defrost theevaporator by giving up this latent heat of evaporation and due to thislatent heat and the heat of condensation in the evaporator saidevaporator is rapidly defrosted. This refrigerant which condenses bycoming in contact with the cold walls of the evaporator is again causedto overllow the accumulator 100 and continue in its cycle back to themotor-compressor unit where it is again evaporated and this cycle iscom-y pleted until the evaporator is defrosted and the temperature ofthe evaporator reaches a predetermined high value. At this time athermostatic control element 180 which includes a thermal bulb 182,bellows 184 'and push-rod 186 interrupts the defrost cycle and restoresthe refrigerating system to normal operation. When the temperature inthe evaporator reaches a predetermined high value the bellows 184expands causing the push-rod 186 to move into engagement with thecontact carrying arm 148 to move the movable contact away from thecontact 154 to interrupt the circuit through the winding 168 of solenoidvalve 176 to thus close the by-pass conduit 174 and restore therefrigerating system to normal operation.

Any suitable type of timing device or counting device may be utilizedfor controlling the operation of the solenoid valve 170. Any suitabledevice which will periodically close the circuit to the solenoid valvemay be utilized for placing the system in condition for automaticdefrosting. Any of the well-known timing devices now in use may besuitable for such purpose. Also, any suitable device which wouldV breakthe circuit through the solenoid valve upon a predetermined hightemperature in the evaporator would be satisfactory for restoring thesystem to normal operation. It' dcsired, a counting device as disclosedin my co-pending application SerialNo. 254,466 filed November 2, 1951,now Patent No. 2,708,348, granted May 17, 1955', may be used for suchpurpose. As to the thermostat 130, any of the well-l nown types now inuse may be used for the normal control of the refrigerating. system.

In Fig. 8 l have shown a modiiedv form of motorcompressor unit 2li@which includes a casing 202. having an inlet 204. Within the casing is amotor 206 having a rotor 2tl8 which carries a cup-shaped memberV 21u.Below the motor is positioned a compressor 212' having an inlet 214.Refrigerant entering the casing 292 moves in the direction of thecup-shaped mein ber 210 and any liquid refrigerant so entering dropsinto said cup-shaped member and due to the rotation of the rotor suchliquid is thrown upwardly into contact with the dome portion of casing202 which causes evaporation of said liquid due to the heat of themotor-cornpressor unit including the heat of its casing. Thus onlygaseous refrigerant enters the inlet 214.

In Fig. 9 there is shown a motor-compressor unit 220 having a casing 222provided with an inlet 224 which receives refrigerant from theevaporator of the refrigerating system. In the casing is shown a motor226 in the upper portion thereof and a compressor 227 is positioned inthe lower part of the casing and provided with an inlet 22S and anoutlet 23). Refrigerant entering casing 222 comes in Contact' withbaffle 232 which causes any liquid refrigerant to il'ow into Contactwith the motor 226, compressor 227 and the inside casing walls toevaporate said liquid due to the heat of the motor and casing whichreceives heat from both the motor and the compressor. Thus onlyrefrigerant gas enters the inlet 228. Under some conditions of operationthe motor-compressor units of the type disclosed in Figs. 8 and 9 may beused to certain advantages.

In Fig. 5 I have shown a rear portion of the evaporator 22 and amodiiied form of control system. This modied form of control systemincludes the timer 144 and the thermostat lZ-il. ln this particularinstance both thermostat and timer bellows are connected to the samethermal bulb 134 by conduit 240 and conduit 24 which is joined toconduit 240. This eliminates the thermal bulb 182 of thermostat 180.

In Fig. 6 l have shown a rear view of the evaporator 22 with bothmodified form of accumulators shown in cross section. In this particulararrangement the outlet accumulator 2553 may be provided with aperforated baffle 252 so that liquid refrigerant entering the aclcumulator 250 would not tend to splash into the inlet of vapor returnconduit 28. In this modication an inlet accumulator 254 is provided withan inlet con nection 256 adjacent the upper portion of the accumulator.ln this embodiment liquid refrigerant entering the accumulator 254during normal operation will tend to move towards the lower part of, theaccumulator254 until the accumulator is substantially lled. In thisaccumulator it will be noted that there is provided a conduit 269 whichextends downwardly into the accumulator to a point adjacent thelowermost portion thereof. At the uppermost portion of the conduit 26!is a small orice 262 through which liquid refrigerant normally ilowsinto the inlet of conduit 3 of the evaporator 22. This small orifice 262is somewhat larger than the small diameter tube 26 so that at all timesliquid refrigerant lnay passthrough that orice to properly permit theilow of liquid into evaporator 22. vThe orifice 262, however, is smallerthan the internal diameter of the tube 260 so that when the solenoidvalve Cil 1:70 is open anygaseous refrigerant' which enters, theaccumulator 254 from the compressor unit will tend to increase thepressure within the accumulator 254 and force liquid from the Ylowerportion of the accumulator into the inlet of the conduit 260 and forcethev liquid refrigerant out of the accumulator 254' during such defrostcycle. This takes place due to the increase in pressure entering theaccumulator 254 at that time.

In Fig. 7 l have shown a modified form of evaporator wherein a singleaccumulator 27u is utilized. In this embodiment the coil of theevaporator 22 may be wound about its side walls theA same as previouslydescribed, however, the rear wall is provided with but a singleaccumulator 27%. ln this embodiment the liquid enters the laccumulator270 through conduit 276 and leaves by outlet conduit 280 which isconnected with the intake of the motor-compressor unit. ln thisparticular embodiment of the invention Vthe particular coils on thewalls of the evaporator' 22 are proportioned as to size so that duringnormal operation some liquid is contained in the accumulator 270 and asubstantial amount of liquid is retained in the walls of the evaporatorduring normal operation. Thus when the solenoid valve is open thegaseous refrigerant leaving the -v motor-compressor unit ows directlyinto the evaporator and the increase in pressure therein and change ofvelocity tends to force the liquid through the evaporator into theaccumulator thereof where it overflows and goes to the motor-compressorunit where it is evap- @rated and returned tothe evaporator to rapidlydefrost the same as is done in connection with the evaporators shown inFigs. 4 and 6.

From the foregoing it will be noted that I have provided a newarrangement for defrosting a refrigerant evaporator of a refrigeratingsystem by conducting liquid refrigerant from the evaporator during thedefrost period to the motor-compressor unit wherein it is evaporated andthis latent heat of evaporation is utilized to increase the vaporpressure and temperature in the evaporator. This is caused by thesensible heat stored in the motor-compressor unit and casing, which heatis generated by mechanical friction and additional heat by electricallosses which are effective to evaporate the liquid which is returned tothe motor-compressor unit and returned to the evaporator in the form ofhot gases which are condensed in the evaporator and the latent heat ofcondensation provides for rapid defrosting of the evaporating element.This is accomplished by a single solenoid valve and an automatic controltherefor to initiate automatic or self defrosting and return the systemto normal operation upon completion of the `defrost cycle. It willfurther be noted that. the flow of refrigerant from the outlet of theevaporator to the interior of the motor-compressor casing isunrestricted, thus denoting that the system is operated without anyrestrictions or other form of controls on the return flow portion of therefrigerating system and that a single solenoid valve controls the inletflow to the evaporator during defrosting and that an inlet accumulatoris provided to provide for additional liquid to ilow to the evaporatorto aid in causing the overflow of liquid refrigerant from the evaporatorso that same is conducted to the motor-compressor unit to increase thepressure and temperature in the evaporator to aid in effectively'andrapidly defrosting the refrigerant evaporator. It will also be notedthat a modified form of my invention consists in proportioning the sizeof the refrigerant conduit forming the major portion of the refrigerantevaporator so that same is slightly larger than the conventional conduitto aid in storing liquid refrigerant in the evaporator during the normaloperation of the refrigerating system so that when the system is on`defrost cycle `such stored liquid is driven from the evaporator conduitinto and out of the accumulator to the motorcompressor unit forevaporation to increase the pressure 9 and temperature in therefrigerant evaporator for effecting rapid defrosting thereof.

Although preferred and modied forms have been i1- lustrated, anddescribed in detail, it will be apparent to those skilled in the artthat various other modifications may be made therein without departingfrom the spirit of the invention or from the scope of the appendedclaim.

I claim:

Refrigerating apparatus comprising a cabinet having a chamber, amotor-compressor unit, an evaporator in said chamber, a condenser, arestrictor, conduit means connecting said unit, evaporator, condenserand restrictor in series circuit relation, said conduit means includingan enlarged portion the inlet of which is connected to the outlet of therestrictor and the outlet thereof to the inlet of the evaporator, saidenlarged portion being in heat exchange relation with said evaporator insaid chamber, and a valve-controlled line by-passing said restrictor andcommunicating with the inlet end of said enlarged portion and beingoperable to interrupt normal ow of liquid through the restrictor andthence to the evaporator,

and to establish modified ow of vaporous refrigerant through said lineto the inlet of said enlarged portion so that the stated ow of vaporousrefrigerant through said line causes refrigerant liquid accumulated insaid enlarged portion during normal operation to ow therefrom throughsaid evaporator and toward said motor-compressor unit.

References Cited in the le of this patent UNITED STATES PATENTS 530,494Chuch et al Dec. 4, 1894 2,069,201 Allison Feb. 2, 1937 2,221,212 Wussowet al Nov. 12, 1940 2,281,770 Hoesel May 5, 1942 2,430,960 Soling Nov.18, 1947 2,440,146 Kramer Apr. 20, 1948 2,452,102 Cocanour Oct. 26, 19482,455,421 Kirkpatrick Dec. 7, 1948 2,555,161 Smith May 29, 19512,564,310 Nussbaum et al. Aug. 14, 1951 2,635,433 Schordine Apr. 21,1953

